CXXC5 Mitigates P. gingivalis-inhibited Cementogenesis by influencing Mitochondrial Biogenesis

Abstract

Abstract Background Cementoblasts are tooth-root surface-lining cells responsible for cementum formation (cementogenesis) and sensitive to Porphyromonas gingivalis stimulation. We have previously proved transcription factor CXXC-type zinc finger protein 5 (CXXC5) participates in cementogenesis. Here, we aimed to elucidate the mechanism of CXXC5 in regulating P. gingivalis-inhibited cementogenesis from the perspective of mitochondrial biogenesis. Methods In vivo, mouse periapical lesions were induced in mandibular first molars by pulp exposure, and P. gingivalis was applied into the root canals. In vitro, a cementoblast cell line (OCCM-30) was induced cemengenesis and submitted for RNA-sequencing. These cells were co-cultured with P. gingivalis and examined for osteogenic ability and mitochondrial biogenesis. Cells with stable CXXC5 overexpression were constructed by lentivirus transduction, and PGC-1α (central inducer of mitochondrial biogenesis) was down-regulated by siRNA transfection. Results Mouse periapical lesions were enlarged and PGC-1α expression were reduced by P. gingivalis treatment. Upon apical inflammation, Cxxc5 expression decreased with Il-6 upregulation. RNA-sequencing showed enhanced expression of osteogenic markers, Cxxc5, and mitochondrial biogenesis markers during cementogenesis. P. gingivalis suppressed osteogenic capacities, mitochondrial biogenesis markers, mitochondrial (mt)DNA copy number, and cellular ATP content of cementoblasts, while CXXC5 overexpression rescued these effects. PGC-1α knockdown impaired cementoblast differentiation dramatically, confirming the regulatory effects of mitochondrial biogenesis on cementogenesis. Conclusions To summarize, CXXC5 is a P. gingivalis-sensitive transcription factor that positively regulates cementogenesis by influencing PGC-1α-dependent mitochondrial biogenesis.